On account of the increasingly occurring shifts in the public electricity supply network towards a supply with renewable power generation sources which are arranged on a decentralized basis, an improved regulation or suitable temporary storage of electric energy is increasingly necessary in order to also be able to operate the electricity supply networks in a stable manner in the case of sharply fluctuating demands or power supplies.
In particular, the temporary storage of electric energy in the form of mechanical energy, for example by means of pressure or a change of the potential energy of a storage medium, is especially suitable for short-term or medium-term energy storage. In this case, the quantities of surplus electric energy which are available in the public electricity supply network are typically used for altering the storage medium with regard to its mechanical energy state. In the case of pump storage power plants, water, for example, is raised to a higher potential energy level by means of suitable pumping devices in order to drive turbines and generators for power generation in a time-staggered manner by means of the water falling to its original level. The current can be fed again into the public electricity supply network and above all can be made available for times at which there is an increased demand for power or regulation.
A disadvantage of the conventional storage power plant technologies, however, is their local limitation with regard to their possible application. Therefore, pump storage power plants in most cases can only be used where the local topography features suitable height differences, for instance. In addition to these disadvantages, an undesirable invasion into the appearance of the landscape and into nature is also frequently cause for complaint. Above all, as a result of the necessary erection of large constructional devices above ground such disadvantages can hardly be avoided.